JPH06270451A - Color image recording method - Google Patents

Abstract

PURPOSE:To prevent a stripe or an interlinear gap from generating in an auxiliary direction, in a serial printer. CONSTITUTION:Recording is performed by allowing to overlap (n+1)th line and (n)th line by a fixed width. This overlapped part OVL is printed by sharing respectively area ratios of 50% by the (n)th line and (n+1)th line. Then a magenta pixel is slid in an auxiliary direction by a 1/2 pitch between pixels adjoining each other in a main scanning direction, a cyanogen pixel and yellow pixel are made into a group of every two pixels in the main scanning direction, those are recorded by sliding by 1/2 pitch for every group in the auxiliary direction. With this construction, since the overlapped part is provided, an interlinear gap is not generated even if paper feed is uneven and density of the overlapped part is not increased, hence this part does not become markedly striped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a color image recording method for a serial printer in which a thermal head moves in a sub scanning direction and a recording paper moves in a main scanning direction.

[0002]

2. Description of the Related Art As a color image recording method, a color thermal recording method, a color ink jet recording method, a color electrophotographic recording method and the like are known. Recently, attention has been paid to a color heat recording method because of the miniaturization of the apparatus and the ease of maintenance. This color thermal recording method includes color thermal recording in which a color image is directly recorded on a thermal recording sheet and color thermal transfer recording in which ink of an ink film is transferred to a recording paper. In the color thermal transfer recording, there are a melt type in which a melted ink is transferred to a recording paper and a sublimation type in which the amount of the ink transferred to the recording paper changes according to thermal energy.

For example, for color thermal transfer recording, a recording head in which a plurality of recording elements are arranged in the main scanning direction is used, one line is printed while moving this in the sub scanning direction, and then the paper is fed in the main scanning direction. A serial printer that prints the next line is often used.

[0004]

However, in the serial printer as described above, unevenness in paper feeding is likely to occur, and therefore the edges of adjacent rows in the main scanning direction overlap each other, and the portion (overlap portion) of the portions overlaps each other. There is a drawback that the density is increased and streaks are formed in the sub-scanning direction, or conversely, a gap is formed between the rows and the streaks of the recording paper appear in the sub-scanning direction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a color image recording method for a serial printer which eliminates streaks and gaps between lines due to unevenness of paper feed.

[0006]

In order to achieve the above object, the present invention relates to one color pixel among three colors of yellow, magenta and cyan, every other pixel in the main scanning direction. Pixel is shifted by a predetermined pitch in the sub-scanning direction and the other 2
For color pixels, the main with shifted in the sub-scanning direction by a predetermined pitch in every two pixels in the scanning direction, n-th row and (n + 1) and row by overlapping only _one sub-line M, _one M The pixels in the sub-line are divided into the first and second groups, the pixels of the first group are printed when recording n rows, and the pixels of the second group are printed when recording (n + 1) rows. It is the one.

[0007]

Since adjacent lines are always printed with a predetermined width overlapping with each other, the lines are not opened and a streak-like gap is not formed. In addition, since the overlapping portions are shared by the respective rows for recording, the density of this portion is not increased and streaks are not formed.
Further, even if the pixels of the three colors are displaced due to unevenness of paper feed, they change while maintaining the complementary color relationship, so that the color tone does not change as a whole even if the color changes microscopically.

[0008]

EXAMPLE FIG. 2 shows a recording state of fusion type thermal transfer recording. As shown in (A), the thermal head 10
Is a plurality of, for example, 64 heating elements 10a, 10b,
, 10c, ... Are arranged in a line in the main scanning direction to print 64 sub-lines forming one row. Each heating element has an elongated rectangular shape having a length L in the main scanning direction and a length D in the sub scanning direction. The length L in the main scanning direction is, for example, 125 μm, and the length D in the sub scanning direction is, for example, 25 μm.

As shown in FIG. 3, the ink ribbon 11 is supplied by a well-known ribbon cassette 12. The ribbon cassette 12 is mounted behind the thermal head 10, and the ink ribbon 11 is slightly pulled out from the ribbon cassette 12 and passed between the thermal head 10 and the recording paper 13. As is well known, on the ink ribbon 11, cyan, magenta, and yellow ink areas are formed at a constant pitch.

During recording, the ink ribbon 11 is brought into close contact with the recording paper 13 from behind by the thermal head 10, and the ribbon cassette 12 is moved together with the thermal head 10 in the sub-scanning direction by the head moving mechanism 14. The thermal head 10 heats the back of the ink ribbon 11 and transfers the melted or softened ink to the recording paper 13. This ink adheres to the virtually represented pixel to form an ink dot. When the recording of one line is completed, the thermal head 10 and the ribbon cassette 12 are returned to the initial positions, and the recording paper 13 is conveyed in the main scanning direction slightly less than the width of one line, and for example, only six sub lines are moved up and down. Lines are overlapped. Reference numeral 15 is a platen roller, and reference numeral 16 is a conveying roller.

As shown in FIG. 2B, the magenta pixel 17 surrounded by the alternate long and short dash line has a rectangular shape with one side being L and the other side being 2L. The length L in the main scanning direction corresponds to the length of the heating element in the main scanning direction, and the length 2L in the sub scanning direction is determined by the energization state of the heating element. In this embodiment, 1
Each pixel has 10 gradations, and one pixel is composed of 10 micro lines. For example, one microline is recorded in the case of one gradation, and two microlines are recorded in the case of two gradations. Pixels adjacent to each other in the main scanning direction have their recording positions displaced by a predetermined distance, for example, 2L / 2 (= L) in the sub scanning direction so that moire and parallel lines do not occur. Each pixel 17 shown in FIG. 2B has an ink dot 18 with an area ratio of 50% as shown by hatching.
Is recorded.

FIGS. 2C and 2D show cyan and yellow pixels, respectively. Similar to the magenta pixel 17, the cyan pixel 19 and the yellow pixel 20 have a length L in the main scanning direction and a length 2 in the sub scanning direction.
L is determined by the energization state of the heating element. Pixels adjacent in the main scanning direction are grouped every two pixels, and the recording position of each group is a predetermined distance in the sub scanning direction, for example, L.
Just shifted. Reference numerals 21 and 22 represent cyan ink dots and yellow ink dots having an area ratio of 50%.

FIG. 4 shows a state in which a gray color having an area ratio of 50% is recorded, which is obtained by superimposing pixels of each color shown in FIG. In an arbitrary first row extending in the main scanning direction, color patterns of black (BK), green (G), magenta (M), and white (W) are periodically generated at a rate of 4 pixels per cycle. In the second column adjacent to this, color patterns of white (W), magenta (M), green (G), and black (BK) are generated. The two adjacent columns have the color patterns arranged in the opposite order, and the adjacent colors have a complementary color relationship. Hereinafter, the eight pixels shown in FIG. 4 are referred to as complementary color compensation units.

FIG. 5 shows a state in which gray with an area ratio of 50% is recorded in the nth row. Six sublines that overlap the (n + 1) th line to be recorded next are recorded in 50% of the complementary color compensation unit, that is, only three of the six colors except W are recorded. This overlap part OVL
Then, the color pattern of only BK appears in the first column, the color patterns of M and G appear in the second column, and these are repeated.

In FIG. 6, the area ratio of the (n + 1) th row is 50%.
The state in which the gray of is recorded is shown. Six sub-lines that overlap the previous n-th row are 50
%, That is, a state in which only three of the six colors except W are recorded. In this state, the color patterns of M and G appear in the first row, the color pattern of only BK appears in the second row,
These are repeated. Reference numeral 10 'indicates a thermal head in which the nth row is recorded.

When both the nth row and the (n + 1) th row are recorded, the overlap portion OVL is recorded in the same pattern and the same density as the non-overlapping row, as shown in FIG. . Here, the paper feeding is uneven,
For example, when the n-th row and the (n + 1) -th row are displaced in the main scanning direction, the color patterns of BK and W appear as shown in FIG. Turns gray, and the overall color tone does not change. Also, n
Even when the line and the (n + 1) th line are displaced in the sub-scanning direction,
As shown in FIG. 8, BK and W color patterns appear, which are also gray when viewed macroscopically.

FIG. 3 shows a fusion type thermal transfer recording apparatus embodying the present invention. The green image data is converted into magenta print data by a look-up table memory (hereinafter referred to as LUT) 25. The LUT 25 outputs print data delayed by 1/2 pitch between adjacent pixels in the main scanning direction. Also, this print data is
The signal form is such that the ink dot length is changed in the range of D to 2L. Also, the overlap part OV
The print data forming L is output by thinning out every other group with two pixels as one group in the main scanning direction so as to be 50% of the complementary color compensation unit. This print data is sent to the thermal head 10 via the contact a of the selector SW2. It should be noted that only the first recorded line and the last recorded line have the overlap portion OVL only on the lower side or the upper side.
The print data is created so as to perform normal recording without thinning out the portion where VL does not occur.

The red image data and the blue image data are
Selectively taken out by the selector SW1, and LUT2
Sent to 6. The LUT 26 is grouped every two pixels in the main scanning direction, and 1 /
The print data delayed by 2 pitches in the sub-scanning direction is output. In addition, this print data has the ink dot length D
The signal form is such that it changes in the range of 2L. The print data forming the overlap portion OVL is thinned out every other pixel in the main scanning direction and output. The selector SW2 is connected to either one of the two LUTs 25 and 26, and prints data to the thermal head 10
Send to.

Next, the recording procedure of the fusion type thermal transfer recording apparatus will be described with reference to FIG. At the time of recording, the platen roller 15 and the transport roller 16 rotate in the direction of the arrow so that the recording paper 1
The leading end of the recording area 3 is fed to the position of the thermal head 10. Thermal head 10 and ribbon cassette 1
2 is moved to the initial position at the left end in the sub-scanning direction, the ink ribbon 11 is fed, and the start end of the magenta ink area is set below the thermal head 10.

The green image data is converted into magenta print data by the LUT 25 and sent to the thermal head 10 via the contact a of the selector SW2. The thermal head 10 is driven according to the print data, and while the thermal head 10 and the ribbon cassette 12 move to the right in the sub-scanning direction, the thermal head 10 heats and pressurizes the ink ribbon 11 from behind to melt it. The recording ink 13
Transfer to. As a result, as shown in FIG. 2B, the length in the sub-scanning direction changes according to the recording density, and
Pixel 1 is an ink dot that is zigzag in the main scanning direction.
Record within 7. Further, in the portion overlapping the next row, every two pixels in the main scanning direction, two pixels are thinned out and recorded.

When the thermal head 10 moves to the right end of the recording area and one line of the magenta image is recorded on the recording paper 12, the heating / pressurization of the ink ribbon 11 is stopped, and the thermal head 10 and the ribbon cassette 12 are stopped. Is moved to the left in the sub-scanning direction. During this movement, the platen roller 1
The recording paper 13 is conveyed by rotating 5 and the next line is conveyed to the position of the thermal head 10. This carry amount is 64
The column length L ₀ (= 6) of the individual heating elements 10a, 10b, ...
6L less than 4L), and adjacent rows are overlapped by this amount. Thereafter, this operation is repeated so that the entire magenta image is recorded on the recording paper 13.

When the recording of the magenta image is completed, the platen roller 15 and the conveying roller 16 are rotated in the reverse direction, and the starting end of the recording paper 12 is returned to the recording start position. The cyan ink area is set on the ink ribbon 11. The red image data is sent to the LUT2 via the contact a of the selector SW1.
At 6, the image is converted into cyan print data. This print data is transferred to the thermal head 1 via the contact b of the selector SW2.
0, and the cyan image becomes 1 as shown in FIG.
It is recorded line by line. In the case of this cyan image,
Similar to the recording of the magenta image, the adjacent lines are fed so that the adjacent lines overlap each other by 6 L, and at the overlap portion OVL, one pixel is thinned out every other pixel in the main scanning direction and recorded. It

In recording a yellow image, the yellow ink area is set on the thermal head 10 and
The selector SW1 is connected to the contact b, and the blue image data is converted into yellow print data by the LUT 26. The yellow print data is supplied to the thermal head 10 via the contact b of the selector SW2, and the yellow images are line by line so that adjacent lines are overlapped by 6 L, similarly to the recording of the cyan image. It is recorded on the recording paper 12.

When the recording of all three colors is completed, the platen roller 15 and the conveying roller 16 are continuously rotated in the arrow direction, and the recording paper 13 is ejected. Overlap part OVL
Is finished with the same hue and density as the non-overlapping portions, and high-quality prints without streaks in the sub-scanning direction can be obtained.

In the embodiment described above, when recording the overlap portion OVL, only 50% of the complementary color compensation unit, that is, only 3 pixels are recorded for 6 pixels excluding W.
In the embodiment shown in FIG. 0, the overlap portion OVL is divided into three lines, and the line closer to the end has a lower recording area ratio. In this embodiment, from the line near the end, one pixel is recorded for six pixels, three pixels are recorded for six pixels, and five pixels are recorded for six pixels. In addition, although each of the above-mentioned embodiments is the melting type thermal transfer recording, the present invention can be applied to the sublimation type thermal transfer recording, the heat sensitive recording, the ink jet recording and the like.

[0026]

As described above, according to the present invention,
The adjacent lines are printed by overlapping each other, and the print of this overlapping part is divided between the upper line and the lower line so that the lines are opened and streak-like gaps are formed. It is prevented that the density of the overlapping portion becomes high and streaks occur. Further, even if the pixels of the three colors are displaced in the overlap portion due to the unevenness of the paper feed, the three colors are changed while maintaining the complementary color relationship, so that it is possible to obtain a print having a good color tone in terms of macro.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state in which an n-th row and an (n + 1) -th row are overlapped with each other and are recorded in a gray area ratio of 50%.

FIG. 2 is an explanatory diagram showing a recording state of each pixel of yellow, magenta, and cyan.

FIG. 3 is a schematic view showing a fusion type thermal transfer recording apparatus for carrying out the present invention.

FIG. 4 is an explanatory diagram showing a color pattern when recording a gray area ratio of 50%.

FIG. 5 is an explanatory diagram showing a state in which the nth row is recorded in gray with an area ratio of 50%.

FIG. 6 is an explanatory diagram showing a state in which the (n + 1) th row is recorded in gray with an area ratio of 50%.

FIG. 7 is an explanatory diagram showing a color pattern when a misregistration occurs in the main scanning direction.

FIG. 8 is an explanatory diagram showing a color pattern when a misregistration occurs in the sub-scanning direction.

FIG. 9 is a flowchart showing a procedure of thermal recording.

FIG. 10 is an explanatory diagram showing another example of the recording method of the overlap portion.

[Explanation of symbols]

 10 Thermal Heads 10a, 10b, ... Heating Element 11 Ink Ribbon 12 Ribbon Cassette 13 Recording Paper 17, 19, 20 Pixel 18, 21, 22 Ink Dot OVL Overlap Part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 9305-2C B41J 3/20 117 C

Claims (1)

[Claims] 1. A recording head, in which M heating elements are arranged in the main scanning direction, is used to change the length of an ink dot recorded in a pixel in the sub scanning direction in accordance with the density, and in the sub scanning direction. Each line composed of M extended sub-lines is divided into at least three lines of yellow, magenta, and cyan.
In a color image recording method of a serial printer for sequentially recording a color image on a recording paper with different types of ink dots, among the three colors of yellow, magenta and cyan,
Pixels of one color are shifted every other pixel in the main scanning direction by a predetermined pitch in the sub-scanning direction, and pixels of other two colors are separated by a predetermined pitch every two pixels in the main scanning direction. Only in the sub-scanning direction, and at the nth line and (n +
1) M ₁ sub-lines overlap with the 1st row, the pixels in the M ₁ sub-lines are divided into first and second groups, and the pixels of the first group are printed when recording n rows. , A color image recording method characterized by printing the pixels of the second group when recording (n + 1) rows.